'Shadow' of oil spill seen in Gulf of Mexico plankton

View full size(NOAA via Wikipedia Commons)Marine diatoms are seen in this NOAA photograph. A paper to be published today says traces of the oil spill can be seen in the Gulf's plankton species.

It is possible to trace oil from the BP spill as it moved through the first several levels of the Gulf’s food chain, starting with the microbes that broke the oil down, according to a scientific paper released today.

That paper, “Oil carbon entered the coastal planktonic food web during the Deepwater Horizon oil spill,” suggests that a faint “shadow” of the oil can be seen in the Gulf’s smallest creatures — plankton and copepods. Those tiny animals ate the microbes that ate the oil.

What’s present in the creatures is not oil. Instead, it is a unique form of carbon typically associated with oil and not otherwise seen in the Gulf creatures, researchers found. Carbon is the primary building block of all life, so it is present in bacteria, copepods, fish and all other creatures.

“We can use this carbon from the oil as a so called bio-marker. We can detect this lighter form of carbon in creatures,” said Monty Graham, a researcher at the Dauphin Island Sea Lab and one of the authors of the paper.

Graham said it was important to note that the research documented carbon from the oil working its way through the food chain, but did not address any of the toxins associated with the oil. It is possible some of those toxins also moved into the food chain using the same pathway, Graham said.

“This paper supports the argument that microbial consumption of oil was just raging out there in the Gulf,” Graham said. “People should really hear this message, that microbes probably did come to the rescue for us on this one.”

Dispersant use was widely debated during the spill. Graham said dispersant use on the surface “almost certainly accelerated the microbial consumption of the oil,” though he was unsure about effects of the more controversial underwater application at the wellhead.

“The water is so much colder down there. It’s hard to say what the effect was. We may never know,” Graham said.

Graham estimated that the spill roughly doubled the amount of carbon present in the Gulf.

“This allowed us to have this natural laboratory where we were able to get a glimpse at the actual role of bacteria in the food web. We were able to see what had eaten the bacteria because they carried the unique marker form of the carbon,” Graham said. “It turns out, bacteria play quite a large role in the ecosystem.”

“We showed with little doubt that oil consumed by marine bacteria did reach the larger zooplankton that form the base of the food chain. These zooplankton are an incredibly important food-source for many species of fish, jellyfish and whales,” said Graham.

“Our next question is, ‘Did all this oil actually supplement the overall productivity of the Gulf?’”